1. Field of the Invention
The present invention relates to a lens barrel, and in particular, relates to a backlash-removal structure for a retractable rotational ring which is moved along an optical axis direction while rotating in accordance with a helicoid.
2. Description of the Related Art
It is essential for structural play (backlash) to exist among movable members of a lens barrel. However, since backlash also adversely affects the movement precision of the movable members, various backlash-removal structures have been proposed. For example, the applicant of the present invention has proposed, in U.S. Pat. No. 7,079,762, a simple, compact backlash-removal structure for a rotational ring which is rotated (rotationally driven) about the optical axis.
In this backlash-removal structure proposed in U.S. Pat. No. 7,079,762, the rotational ring rotates at a fixed location without changing position in the optical axis direction. However, a retractable rotational ring which rotates and moves along an optical axis in accordance with a helicoid is often used as a movable member of a lens barrel instead of the above-mentioned movable member (rotational ring) which rotates at a fixed location.